Particulate absorbents (e.g., talc, pearlite) have been used as liquid waste absorbents since ancient times. However, inorganic absorbents are generally virtually non-selective and hence unsuited to the selective absorption of organic material in the presence of water. This lack of selectivity makes them unsuitable for separating or recovering minor proportions of organic contaminants from aqueous systems, e.g., dioxins from stream beds or oil slicks from ponds, rivers and/or coastal waters.
Organic (polymeric) absorbents have not heretofore been widely used, despite their relatively selective absorption of organics, because of the low absorption rates displayed by larger, hard, non-elastomeric particulate and the tendency of small particular organics to be wind-dispersed as a consequence of their low bulk densities and/or specific gravity.
In recent years, elastomeric particulate material and plasticized (partially) aggregated elastomeric particulate have been found to provide a partial solution to the problem of absorbing limited quantities of organics in the presence of water, in undisturbed and agitated areas, respectively. However, most elastomers, with the notable exception of polynorbornene, have relatively low organics absorption limits, particularly if the resulting composite must resist leakage, i.e., bleeding, while undergoing compression during transport and/or in landfill disposal.
The success of polynorbornene in achieving certain of the ideals of an absorbent has been recently reported in the paper by L. M. Flaherty et al., "Sorbent Performance Study for Crude and Refined Petroleum Products" presented at the 1989 Oil Spill Conference, under the heading "Emerging Technologies" (pp. 155-160).
Despite its relatively selective absorption of organics, this polymer suffers from relatively rapid deterioration of its absorption capabilities under environmental exposure and the tendency of even lightly plasticized material to quickly agglomerate into large, low absorption rate accretions. The reason for this rapid and significant volumetric absorption capability loss upon exposure is unknown but may be related to air oxidation, accelerated by water and certain metals. Conventional antioxidants such as phenolics or hindered amines have proven partially successful in extending polynorbornene's useful life as a waste collector, but the leachability of such antioxidants and their high bioactivity limit their practical application.